1. Field of the Invention
This invention relates to terminal crimping devices and more particularly to a terminal crimping device which is used to crimp the clasping lugs of an electrical terminal over an electrical wire to fixedly connect the terminal to the wire, for instance, no matter what the diameter of the wire is.
2. Prior Art
An electrical terminal is well known in the art, which is connected to an electrical wire by crimping it. The electrical terminal has crimping portions at its rear end portion which are used for fixedly holding an electrical wire. With an electrical wire placed on the rear end portion of the electrical terminal, the crimping portions are bent inwardly in such a manner as to fixedly embrace the electrical wire (cf. Examined Japanese Patent Application Publication No. Sho. 55-37840).
In order to fixedly connect an electrical terminal to an electrical wire, a terminal crimping device as shown in FIG. 5 is used as follows: The device comprises: an upper die, namely, a pressing toothed upper die 1; and a lower die 2. An electrical terminal 3 is set on the lower die 2, and an electrical wire 4 is placed between the clasping lugs 3a and 3a of an electrical terminal 3. Under this condition, the toothed upper die 1 is pushed against the lower die 2. As a result, the clasping lugs 3a and 3b are bent inwardly in such a manner as to embrace and bite the electrical wire 4.
The pressing toothed upper die 1 has an axially symmetrical recess 5 which consists of right and left guide walls 1a and 1a which are sloped and opened towards the lower die 2, and right and left pressing curved walls 1b and 1b which merge with the right and left guide walls 1a and 1a, respectively. The pressing toothed upper die 1 is slid downwardly as indicated by the arrow P until the lower die 2 comes in the recess 5. When the pressing toothed upper die 1 and the lower die 2, which have been engaged with each other in the above-described manner, are slid relative to each other, the clasping lugs 3a and 3a substantially U-shaped in section are bent inwardly while sliding on the sloped guide walls 1a and 1a. Thereafter, the clasping lugs 3a and 3a are sufficiently crimped by the pressing walls 1b and 1b while being guided by the latter.
FIG. 6 shows an electrical terminal which has been crimped over an electrical wire 4 by the above-described conventional terminal crimping device. In the case of FIG. 6, the electrical wire 4 connected to the electrical terminal is small in diameter (size).
In the case where an electrical wire to be connected to the electrical terminal with the device is relatively small in diameter, as shown in FIG. 6 a crimp height Y is provided between the toothed upper die 1 and the lower die 2 when those dies 1 and 2 are engaged with each other to crimp the electrical terminal over the electrical wire.
The above-described conventional terminal crimping device is disadvantageous in the following points:
In the case where an electrical wire to be connected is relatively large in diameter, as shown in FIG. 7 the crimp height Y is larger than in the above-described case where the electrical wire is relatively small in diameter. When the crimp height Y is large, then there is formed a gap X between the lower die 2 and each of the sloped guide walls 1a because the recess 5 formed by the sloped guide walls 1a and 1a is gradually wider towards the outer end face of the toothed upper die 1. Because of the gaps X on both sides of the lower die 2, burrs 6 are formed on the back of the electrical terminal 3.
The burrs 6 thus formed make it impossible to measure the crimp height of the terminal thus connected. Therefore, it is impossible to measure the degree of tightness of the terminal, and accordingly it is also impossible to determine whether or not the electrical wire has been sufficiently connected to the electrical terminal. Moreover, the burrs are liable to crack the terminal. In addition, in inserting the electrical terminal thus connected into the housing, the burrs may damage the latter or make it impossible to insert it into it.